This invention relates to a method of analysis which yields a description of a video signal (hereinafter referred to as a profile or statistical profile), which relates the signal content to its likely perceptual significance.
Proven applications of the profile analysis include noise filtration, data compression, motion detection, object tracking and video special effects.
As a background to the invention, it will be understood that digital video is a major growth area, both in home entertainment and in business. Digital video is at the heart of up and coming technologies such as video conferencing and video telephony.
The main problem with digital video is the amount of data needed to represent even a small number of frames. Hence, processes that compress this data or improve the performance of other data compression techniques will play a crucial role in its development and successful application. This invention proposes a method of analysis which yields content and significance information in the form of a statistical xe2x80x98profilexe2x80x99. This information can be used directly by CODECs to regulate the selection of blocks, regions or other image components contained within a video signal, or the selection of appropriate coding techniques. Alternatively it can be used to control a filtration process which selectively removes noise from a video signal.
Within any digital video signal, there is a considerable amount of noise. This is likely to be true even in high quality broadcast systems but is a particular problem in low cost solutions such as those which might be used, for example, in a video telephone. Noise significantly degrades the compression performance and the quality of the output from most video compression CODECs.
The method of the invention is intended to complement rather than necessarily replace existing compression, filtration, image processing and analysis techniques.
According to the invention, there is provided a method of analysing a digital video signal to generate a statistical profile thereof, according to which corresponding pixels in consecutive frames and/or neighbouring pixels in the same frame are examined for relative brightness and/or relative colour and stored as a function of the amount of change and the number of and/or pattern of changed neighbouring pixels, thereby to produce a pixel map, and the mapped pixels are categorised into classes ranging from zero score for zero change to the highest score for the greatest change, enabling the classification, i.e. statistical profile, to be utilised during further processing of the digital video signal.
The method may be performed by means of dedicated hardware or by programmed computerised apparatus.